Increase calcium intake and maintain bone strength Support bone strength, muscle function, and healthy immune system function with Ostelin Calcium & Vitamin D3 Tablets 300 Exclusive Size. Ostelin Calcium & Vitamin D3 is formulated for bone strength and density. Ostelin Calcium & Vitamin D3 assists with healthy bone development in teens, while maintaining healthy bone density and strength in adults. Vitamin D3 increases calcium absorption in the body* and supports healthy immune system function and maintains healthy muscle function. Adults and Teens 13+: take 2 tablets daily, or as directed by your healthcare professional.